Modem security systems have become increasingly sophisticated. Today, they are able to monitor for break-ins, smoke, fire, earthquakes, chemical releases and a host of other conditions requiring appropriate response. Often, these security systems interface not only with alarms to alert people of the emergency condition but also with remote monitoring facilities and emergency response teams such as the police or fire departments. In addition, these security systems can control the activation of sprinklers, the release of doors and other control functions.
Upon the detection of smoke, fire or other emergency conditions, it is especially critical to release doors, especially in crowded commercial establishments. The failure to release a single door can cause crowd panic and has in some instances resulted in the loss of life. For this reason, many methods have been applied to releasing doors under emergency conditions.
Some representative examples include: (1) U.S. Pat. No. 6,265,979, titled “Earthquake Sensing Device,” to Chen and others; (2) U.S. Pat. No. 6,049,287, titled Door with Integrated Smoke Detector and Hold Open,” to Yulkowski; (3) U.S. Pat. No. 5,429,399, titled “Electronic Delayed Egress Locking System,” to Geringer and others; and (4) U.S. Pat. No. 4,803,482, titled “Exit Control and Surveillance System,” to Verslycken. Each is incorporated herein in their entirety and each is described briefly in turn.
U.S. Pat. No. 6,265,979 generally teaches a device for detecting an earthquake and for controlling emergency functions. The device measures both horizontal and vertical vibrations. Based upon those measurements, the device determines whether an earthquake has occurred and if so releases doors.
U.S. Pat. No. 6,049,287 generally teaches a door control device that automatically releases a door upon detection of smoke. The door control device is physically mounted on the door and releases associated electronic locks.
U.S. Pat. No. 5,429,399 generally teaches a door control device that receives various alarm signals including smoke or seismic activity. In response to these alarm signals, the door control automatically releases associated door locks.
Finally, U.S. Pat. No. 4,803,482 generally teaches a door release and surveillance system. The door release is requested by a person by pressing a release lever at the door. This sends a signal to a central control location. The central location can monitor the door through a surveillance system. In response to the request it can elect to permit the door to release. Alternatively, it can delay or prevent the door to release should the central control location determine that there is not an emergency condition and the door should remain locked.
While each of the above discussed patents describes methods of releasing doors in response to alarm conditions such as fire or seismic activity, none address well or even appear to recognize the importance of distinguishing between different types of seismic activity. Specifically, both an explosion and an earthquake will cause vibrations but the two require different responses.